1. Field of the Invention
The present invention relates to a manhole cover/frame exchange method in electric power supply systems, telecommunication systems, water supply and drainage systems and the like.
2. Brief Description of the Related Art
In conventional construction works for exchanging manhole covers/frames of electric power supply systems, telecommunication systems, water supply and drainage systems and the like, paved roads around manholes are cut in a square or in a circle shape perpendicular to the ground by utilizing cutters or core-cutters with straight blades. Cut portions around the manholes are removed, removed portions are filled with mending materials and pressed by roller machines.
A Japanese published patent No. 2-15687 discloses a paved road cutting/removing method including a cutting step to cut a portion of a paved road to be removed into a plate and a removing step to lift the cut portion in which one or two anchor bolts are buried. The cut portion shows a circular or rectangular plate shape. When the cut portion is the rectangular plate, at least two facing sides of the plate are tapered toward the ground.
However, in the above-mentioned conventional method, when the paved roads are cut in the square shape, edged corners are formed (see FIG. 4B). Unfilled vacancies are apt to be formed in these edged corners during a mending step, since fillers as mending materials are filled into not all over the edged corners. Since the paved road is cut perpendicular to the surface of paved road in the circular cutting as well as in rectangular cutting, mended portions are supported only by a frictional force F of mending materials against perpendicular walls of cut portions of the paved road. Consequently, mended portions are apt to sunk and gaps are formed. Mended portions are further sunk due to penetrated rainwater into these gaps, which might cause an accident.
In the case of the square cutting, more mending materials are required in order to fill the edged corners shown in FIG. 4B.
As mentioned above, inconveniences such as sunk and/or irregular surfaced portions are caused in the paved road with the passage of time, unless a step to fill mending materials into edged corners and a rolling step to press filled portions with mending materials, are performed.
Besides, in conventional mending methods there are problems such as difficulties to shorten a mending term including a cure time of conventional filling materials to a large extent and to suppress noises generated during the mending process.
The present invention is carried out in view of solving the above-mentioned problems to provide a manhole cover/frame exchange method capable of minimizing the size of a portion to be mended, of eliminating a pressing step by a roller machine, of eliminating/reducing steps and mending terms and of suppressing vibrations, noises and the like during the mending process.
The above-mentioned problems are solved by the following constitutions by the present invention.
(1) A manhole cover/frame exchange method for exchanging manhole cover/frame of an electric power system, a telecommunication system, a gas supply system and a water supply and drainage system comprising steps of: cutting a portion of a paved road around the manhole cover/frame spherically; removing the spherically cut portion; filling a self-curing highly fluid non-shrink filler into a spherical hollow space formed by the removing step, and filling a surface layer material over the self-curing highly fluid non-shrink filler, wherein: a pressing step by a roller machine is eliminated.
(2) The manhole cover/frame exchange method according to (1), wherein: the highly fluid non-shrink filler mainly consists of mortars containing metallic non-shrink materials such as calcium-sulfo-aluminates.
(3) The manhole cover/frame exchange method according to (1), wherein: the highly fluid non-shrink filler mainly consists of mortars containing non-metallic non-shrink materials, but not containing metallic aggregates.
(4) The manhole cover/frame exchange method according to (1), wherein: a material containing fibrous materials is employed as the surface layer material.
(5) The manhole cover/frame exchange method according to (1), wherein: a reinforcing iron rod network is arranged when the highly fluid non-shrink filler is filled.